(By Gregory E. Maggs, Professor at George Washington University and Former Clerk to Justice Thomas)
The term “federalism” refers to the division of power between the federal government and the state governments. A fundamental principle of federalism, as expressed most clearly in the Tenth Amendment, is that the Constitution confers certain limited legislative powers on Congress and reserves all other legislative powers to the states. For example, Congress has the exclusive power to regulate subjects like immigration, bankruptcy, and patents and copyrights because the Constitution grants these powers to Congress. In contrast, matters of family law, inheritance, and so forth are almost exclusively governed by state law because the Constitution gives Congress little or no power to regulate these subjects. This division of powers generally allows the states to determine what is best for local conditions, while leaving regulation of a limited number of subjects of national concern to Congress.
The Supreme Court, however, has not strictly guarded the constitutional lines between federal power and state power. On the contrary, various lines of cases have shifted the balance of powers, allowing the federal government to regulate more and the state governments to regulate less. During his twenty-five years on the Supreme Court, Justice Thomas has consistently disagreed with this expansion of federal power on grounds that it departs from the text of the Constitution. Three examples illustrate how Justice Thomas’s views have differed from those of the majority of the Court.
Preemption of State Law under the Supremacy Clause
The first example of how Justice Thomas has opposed expansion of federal power concerns the Supremacy Clause. The Supremacy Clause says that federal law “shall be the supreme law of the land; and the judges in every state shall be bound thereby, anything in the Constitution or laws of any State to the contrary notwithstanding.” Under this provision, when a valid federal law conflicts with a state law, the federal law controls. For instance, suppose a federal law requires banks to give their customers credit for deposited checks in two business days, while a state law says that banks must give their customers credit in a reasonable time. Under the Supremacy Clause, because the federal law and state law are different, the federal law “preempts” the state law—meaning that the federal standard of two days controls. Federal preemption is a very important aspect of federalism; every year, courts find that federal laws preempt hundreds of state laws, effectively limiting state efforts to legislate.
Federal preemption of state law under the Supremacy Clause is seldom controversial when state laws actually conflict with valid federal laws. But in a series of cases, the Supreme Court has held that federal laws may implicitly preempt state laws when the state laws pose an obstacle to Congress’s “purposes and objectives” even if the state and federal laws do not actually conflict with each other. For example, in Arizona v. United States, the Supreme Court held that a federal law that imposed civil penalties on aliens who seek or engage in unauthorized employment preempted a state law that imposed criminal penalties for the same conduct. Although the state law did not conflict with any federal law—it would be possible to impose both civil and criminal penalties—the Court held state law “was an obstacle to the regulatory system Congress chose” because Congress chose not to impose criminal penalties.
Justice Thomas dissented, explaining that the “ ‘purposes and objectives’ theory of implied pre-emption is inconsistent with the Constitution because it invites courts to engage in freewheeling speculation about congressional purpose that roams well beyond statutory text.” Justice Thomas based his narrower view of preemption on what the Constitution actually says. “Under the Supremacy Clause,” he reasoned, “pre-emptive effect is to be given to congressionally enacted laws, not to judicially divined legislative purposes.” Because the federal law did not actually conflict with the state law, Justice Thomas concluded that the federal law did not preempt the state law.
Congress’s Power under the Commerce Clause
The second example concerns Congress’s powers under the Commerce Clause, which grants Congress the power to “regulate Commerce . . . among the several States.” Through this power, Congress can pass laws governing matters such as the interstate sale and transportation of goods and services, including the operation of interstate railroads, national commodity markets, and so forth. More controversially, since 1937, the Supreme Court has held that Congress also may regulate intrastate economic activities—i.e., matters that take place wholly within one state, such as farming, mining, manufacturing, and so forth—if those matters in the aggregate might have a substantial effect on interstate commerce. This so-called “effects test” (also referred to as the “affectation doctrine”), if unquestioningly followed, would enable Congress to regulate most activities because most activities, when multiplied across the whole country, might have a substantial effect on interstate commerce.
An illustration of the “effects test” and Justice Thomas’s disagreement with it appears in the case of Gonzales v. Raich. In that case, the majority of the Supreme Court held that Congress had the power to prohibit a cancer patient from growing marijuana in her own home and using it for legitimate medical purposes as allowed by the applicable state law. The majority of the Court recognized that home cultivation and smoking of marijuana was not interstate commerce, but held that Congress could regulate the cancer patient’s activities because “Congress had a rational basis for concluding that leaving home-consumed marijuana outside federal control would . . . affect price and market conditions.” The theory was simply that people who grow marijuana at home would not purchase marijuana on the interstate market. Justice Thomas dissented. His position was simply stated: “Respondents’ local cultivation and consumption of marijuana is not ‘Commerce . . . among the several States.’ By holding that Congress may regulate activity that is neither interstate nor commerce under the Interstate Commerce Clause, the Court abandons any attempt to enforce the Constitution’s limits on federal power.” Justice Thomas disagreed with the “effects test” because it was not rooted in the text of the constitution, was highly malleable, and easily manipulated. The consequence of applying the effects test, in his view, was to prevent states “from devising drug policies that they have concluded provide much-needed respite to the seriously ill.”
The Dormant Commerce Clause Doctrine
The third example concerns the so-called “Dormant Commerce Clause Doctrine” (also known as the “Negative Commerce Clause Doctrine”). In a series of cases, the Supreme Court has held that the grant of power to Congress to regulate interstate commerce implicitly limits commercial regulation by state legislatures even when Congress has not enacted conflicting legislation. Specifically, the Supreme Court has held that, while states may regulate commerce to some extent, states cannot impose an excessive burden on interstate commerce, cannot discriminate against interstate commerce, and cannot regulate subjects which, if they are to be regulated at all, must be regulated by a uniform national standard. These limitations do not appear in the text of the Constitution or in any statute; instead, the Court has devised them based on what it has considered the needs of the federal system.
For instance, in Camps Newfound/Owatonna v. Town of Harrison, the Supreme Court struck down a state law that generally granted property tax exemptions to charitable institutions but that denied the exemption to charitable institutions that operated principally for the benefit of nonresidents of the state. The Court held that the state law violated the Dormant Commerce Clause doctrine because it discriminated against interstate commerce by treating institutions differently depending on whether they served residents or non-residents. Justice Thomas dissented on grounds that the Dormant Commerce Clause doctrine “has no basis in the text of the Constitution.” Justice Thomas explained that “[c]onflict pre-emption only applies when there is a direct clash between an Act of Congress and a state statute, but the very premise of the negative Commerce Clause is the absence of congressional action.” Justice Thomas asserted that “the Court should confine itself to interpreting the text of the Constitution, which itself seems to prohibit in plain terms certain of the more egregious state taxes on interstate commerce . . . and leaves to Congress the policy choices necessary for any further regulation of interstate commerce.”
These examples show three ways in which the Supreme Court has departed from the balance of federal and state powers established by the text of the Constitution and how Justice Thomas has disagreed with the Court’s decisions. While Justice Thomas’s dissenting views have not changed the law, their logic and consistency may limit future erosion of federalism in the United States.
 Professor of Law, The George Washington University Law School. I served as a law clerk for Justice Thomas in the October 1991 Term.
 U.S. Const. amend. 10 (“The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people.”).
 Id. art. I, § 8, cl. 4 (“The Congress shall have Power . . . To establish a uniform rule of naturalization, and uniform laws on the subject of bankruptcies throughout the United States.); id. cl. 8 (“(“The Congress shall have Power . . . To promote the progress of science and useful arts, by securing for limited times to authors and inventors the exclusive right to their respective writings and discoveries”).
 Id. art. VI, cl. 2.
 132 S. Ct. 2492 (2013).
 Id. at 2504.
 Id. at 2524 (Thomas, J., dissenting).
 U.S. Const. art. I, § 8, cl. 3.
 See United States v. Lopez, 514 U.S. 549, 558-59 (1995) (reviewing the history of the “effects test”).
 Gonzales v. Raich, 545 U.S. 1 (2005).
 Id. at 19.
 See id.
 Id. at 57 (Thomas, J., dissenting).
 See id. at 67-71.
 Id. at 74.
 See Gregory E. Maggs & Peter J. Smith, Constitutional Law: A Contemporary Approach 285 (3d ed. 2015).
 520 U.S. 564 (1997).
 See id. at 579.
 Id. at 610 (Thomas, J., dissenting).
 Id. at 616.
 Id. at 620.